Tube and plate type heat exchanger and method of making



March 16, 1954 L. WEISS 2,672,324

v TUBE AND PLATE TYPE HEAT EXCHANGER AND METHOD OF MAKING Filed Sept. 29, 1948 FIG-.I.

' 4, 12! I G l i Q INVENTOR; LOU/S WEISS,

WNEX 7" Patented Mar. 16, 1954 TUBE AND PLATE TYP AND METHOD Louis Weiss, St. Louis, Mo. Application September 29, 1948, Serial No. 51,780

6 Claims.

This invention relates to improvements in assembly of plate and tubing elements, and more particularly to an improved structural combination of tubing and surface-extension structure,

particularly adapted for heating, cooling and similar fields of usage. The present improvements further relate to an improved method of forming structures of the kind referred to, involving several novel steps of assembly.

Numerous attempts have heretofore been made to produce an extended-surface tubing at a moderate cost and in such manner as to attain a desirable proportion of heat absorption and radiation area, to the cross section of the tubular elements. Most such attempts heretofore made, involve the application of perforated fins or the like, either in groups or individually, over a length of tube, or the insertion of straight lengths of tubing into the perforated elements, thus necessitating the forming of a sinuous or convolute tubing structure, after application of the surfaceextending elements thereto. This obviously results in a time-consuming series of assembly steps, with consequent high costs. Furthermore, the conventional application of fins and similar plate or sheet elements to thermal exchange tubing, has heretofore in all cases known to this applicant, resulted in vastly augmented dimensions of the tube assembly, Particularly in refrigeration installations this detraction from useful cooling space, is a serious shortcoming. It is accordingly a principal object of the present invention to obviate the noted inadequacies of present structure and steps of their manufacture, and to attain a tube and plate assembly which need not be of materially greater thickness or transverse dimension than the outside diameter of the tubing, and yet is of such nature that the tubing may be entirely preformed, and thereafter assembled to the surface-extending elements, such as a plate or sheet.

A further object of the invention is realized in a structure of the kind noted, in which the tubing is or may be tightly gripped within a formed plate structure, resulting in an improved structural relation of, and thermal path between the tubing and plate structure, irrespective of any welding, soldering, brazing or like operations.

Yet another object of importance attained by the present improvements consists in a sturdy, rigid unit structure in positively and rigidly secured against vibration and bending stresses, and as well is desirably pro? tected against liability of deformation by impact.

A still further noteworthy advantage, realized by the present improvements, is the production of which a tubing preform is E HEAT EXCHANGER OF MAKING a preformed tubing and plate structure which is or may be produced as a unit, ready for assembly in any of a variety of heat exchange devices, as in certain heating installations, and very importantly in many refrigerated structures such as cooling cabinets, food refrigerators, beverage coolers and the like, such units being of an unusually rigid character and susceptible of usage selectively as partitions, shelving, and as closure elements of refrigerated chambers,-t0 note but a few of the many fields of possible usage.

Stated more particularly with respect to the novel method and steps thereof preferred for production of the improved tube and plate assembly, such method enables a mechanical assembly of a preformed tubing of sinuous shape, directly into preformed seats therefor, in a formed plate structure substantially embracing the tubing.

The foregoing and numerous other objects and advantages of the invention will more clearly appear from the following detailed description of a preferred structural example and a preferred method of assembly, particularly when considered in connection with the accompanying drawing, in which:

Fig. 1 is a planar sheet of metal, such as steel, which has been perforated in a predetermined pattern and in such manner that upon forming the sheet, there will result a plurality of seats or channels for the reception of a metal tubing;

Fig. 2 is an end view, isometric in nature, of the sheet of Fig. 1 as same appears after corrugation;

Fig. 3 is a view showing in end elevation, a preformed element of tubing, and a corrugated sheet, in process of assembly;

Fig. 4 is an end elevation showing the elements of Fig. 3, following their assembly;

Fig. 5 is an isometric plan view of one face of a fully assembled combination of tubing element and plate element, and

Fig. 6 is a side elevation on a reduced scale, illustrating one manner of commercial usage of a unit such as shown by Fig. 5, in a cabinet type of cooling unit.

Referring now by characters of reference to the drawing, in Fig. 1 the sheet is generally indicated at it and may for convenience in processing, be provided with a number of lines I I shown as mutually parallel, and which as will appear, constitute bending or folding lines as a guide to the formation of sheet It. The several lines .II are or may be substantially equidistantly spaced across the sheet, although certain pairs of the lines ll.

if desired and as shown, certain somewhat wider spaces l2 are defined by fold lines define, in a formed sheet such as shown by Fig. 2, a series of parallel ridges or corrugations l3, these being of a substantially rectangular or square section in the example shown, the ridges or corrugations 13 being intervened by longitudinal recesses or valleys M.

In Fig. 1 there will be seen a series of rows of perforations each perforation being indicated generally or as a whole, at i5. Each such perforation is shown as being of a generally dumb bell shape, and consists at each of its ends, of a substantially circular aperture it, these apertures being, by preference, connected by a neck or slot H, the width of which is shown and preferred to be somewhat less than the diameter of portions IE. It will further appear that the perforations i5 are arranged in rows, three such rows being shown in Fig. 1.

The arrangement of the perforations with respect to the lines H is preferably such that each a of the end circles it lies substantially tangent to a pair of adjacent lines H, and the corrugation of the sheet at the perforation, is so effected that, utilizing corrugations of the type shown by Figs. 2 and 5, the connected pair of circular apertures I6 lie in register in the spaced opposite sides of one of the corrugations. It is further a preference so to proportion the diameter of the circular apertures i5 and the height or depth of each corrugation, that the apertures open into the top surface of the corrugation, which is bridgingly incised by the slot ll, in fact a plurality thereof, in the structure shown. The arrangement described results in the plurality of coil seats or channels, each such seat for a given rectilinear pass of the coil, being constituted by one of the dumb bell perforations it.

In the present example, a coil of tubing for example of flexible copper stock, generally indicated at 2!}, is formed of a series of linear passes 2i, end-connected by half-circular turns as indicated at 22. By utilization of present improvements such a coil shaped in the manner noted, or in any of a number of other suitable shapes, may be completely formed prior to its application to the sheet or plate, which when formed up and corrugated, results in the structure generallyidentified at 23, as shown by Fig. 2. In this structure the formed sheet includes substantially vertical sides 2 of each corrugation and opposite corresponding sides 25, sides 24 and 25 being bridged by the relatively flat top [3 of each corrugation or ridge. It has been noted that the several valleys it, in an angulate type of corrugation as shown and preferred, are of open top rectangular form, constitute inverted corrugations, and are defined by the planar bottom portions 2%, which with a pair of the adjacent corrugation sides 24% and 25, define the valleys l4 as noted.

it should be indicated as apreference but without restriction, that the apertures it be of such diameter as to conform closely to the outside diameter of the tubing of element 28, particul'arly the horizontal passes 2% thereof. This assumes, of course, that the tubing is of circular cross section, and that the apertures it are likewise of circular shape. But for cost and other production consideration, it is obvious that, if tubing of other than circular section be employed, the apertures 16 should conform substantially thereto. By reason of the aforesaid proportion of apertures [8 to outside diameter of the tubing 2U, it will later herein appear that the tubing in assembly with the sheet, is tightly gripped,

and in fact, may be slightly constricted by and in the zones of its engagement with the marginal metal about the several apertures it. This effect is enhanced to the extent that apertures it may even be of slightly smaller diameter than the O. D. of the tubing. Assuming the latter to be formed of flexible copper, the tubing may be very slightly penetrated by the edges of the metal about the apertures, and thus under a slight compression in assembly, and thereby lteep the tubing accurately and tightly spaced within the corrugations of the plate, and at the same time assure a plenary thermal path between the tubing and plate elements. This feature, as has been found in commercial usage, will in many cases obviate any necessity for the-use of soldering, brazing, welding or the like, for permanent assembly of the tubing to the plate structure.

There will be later herein described the method of applying and assembling the preformed tubing to the plate structure 23, in such manner that the horizontal passes 21 of the tubing accurately align with the several horizontal rows (Fig. 1) of the perforations it. It is sufficient for present discussion to note that the tubing is brought snugly into said slots and after reposing therein, may if desired, be permanently assembled through the use of a mounting strap 21 or a plurality thereof, spaced at intervals over the assembled coil structure and welded to, and so as to overlie, certain of the flat top portions i3 of the corrugations. A few such zones of welding are indicated at at (Fig. 5), and the strap elements 2'5 are shown as provided with outturned end portions 3i apertured to receive mounting bolts, screws or the like.

As noted, the unit as described and consisting of a combined plate and coil assembly, may be used for a variety of thermal exchange and other purposes, a typical such usage in a refrigeration unit being suggested by Fig. 6, wherein acompleted unit of planar type and indicated at E2 is arranged vertically as a partition element in and across a cooling chamber 33? of a box type cooler generally indicated at St, and provided with insulated walls 35.

Proceeding now to a more complete discussion of the several steps of a preferred method suitable for producing the several elements described, and the assembly thereof, a first stage or step will usually consist in scoring or otherwise marliing the planar sheet it to provide the lines ll thereon, indicative of the zones of folding or forming. The use of such lines is of course optional, these being unnecessary with certain types of equipment in which accurate indexing is provided for. Assuming, for convenience of present discussion that the lines H are ruled on the sheet iii, a subsequent step consists in the perforation of the several portions 65. While this may be done by multiple drilling of the circular apertures it and slotting operations to provide the somewhat more narrow portions ll between and connecting the apertures it, perforations [5 are preferably punched in the lines and rows in the general pattern suggested by Fig. 1.

A subsequent step in forming up the now perforate sheet ii] to result in the corrugated structure 23, consists in imparting to the sheet H} a series of right angular folds along the lines 1 i to result in the rectangular, or perhaps square section of the corrugations as shown. Metal or other conducting material of such a gauge is selected that the now corrugated sheet is susceptible of deformation, as by bending as shown by Fig. 3,

out of its original and normal'plane. This may be done by the use or with the aid of suitable holding tools or jigs (not shown) Such bending or breaking is importantly effected in the direction shown by Fig. 3, i. e. in a manner to widen the slotted portions originally designated as ll, sufficiently to enable the insertion thereinto, and usually one at a time, of. the successive passes of the preformed tubing structure 28. With particular reference to Fig. 3 as to this step, the most noticeable deformation of the corrugated structure takes place along lines indicated by the reference characters 36 with the noted eifect of markedly widening the line or row of slots I? along the break line, and sufficiently to enable insertion of the selected pass 2! of the coil into such channel or slot. It will have been noted that this step is preferably conducted as a series of successive such steps, one such line of bend being indicated at 535-416 in Fig. l, for clarity of description. As the successive passes 2! are inserted in the slots along a given line 36-36, the portion of the plate deformed to permit such insertion, is restored to a substantially planar form. Thus it is seen that, when the final such pass of tubing is inserted, the entire assembly has once again assumed its original planar form as will appear from Fig. 4, showing the appearance of the assembled tube and plate unit in an edge view.

But for any pressure, loading or impact on the assembled tubing and plate unit in service, it will adequately retain its completed planar form without any tendency of the assembled elements to part. However, since it is usually a matter of convenience in mounting the units such as shown by Fig. 5, to provide bracket elements thereon, permanence of assembly is still further assured by the use of strap elements 21 having the function of mounting brackets as shown by Fig. 6. It will now have become obvious that with one or more of the strap members 21 welded as at 30, or otherwise secured in place, it becomes impossible for the corrugated plate member 23 to be deformed under any normal loading, from its original shape, assumed to be planar. In fact repeated tests and usage indicate that the presence of the tubing as locked in place in its seats in the plate, acts to stiffen the plate, as the plate does the tubing, and thus to result in a unitary structure of rugged characteristics and long life.

Assuming that the diameter of apertures IE3 is no greater than, or even slightly less than the outside diameter of the tubing 2l22, it will have appeared that the restoration of the successive zones of the corrugated plate 23 to planar form, after application of the tubing into the tube channels of the plate, will cause the sides of each aperture is tightly to embrace and engage, in fact, optionally slightly to penetrate the tubing walls, but of course incompletely. Experience has shown that the tubing is thus very tightly secured in position in the plate seats, so long as the assembled unit maintains approximately its intended shape.

For convenience of description of the particular selected example, reference has been made entirely to a corrugated sheet or plate in which the corrugations are distinctly angulate. Such description should not be construed as precluding the use of ridges or corrugations of other than the shape shown.

Although the invention has been described by making detailed reference to certain preferred elements and to a proven method of production and assembly of such elements, the detail of description is to be understood solely in an instructive, rather than in any limiting sense, because of the numerous variants possible within the scope of the claims hereunto appended.

I claim as my invention:

1. The hereindescribed method of forming and assembling a sheet material and a tubing, to ex-, tend the surface of the latter, which consists in perforating a sheet of thermally conductive metal to provide therein one or more rows of apertures each of dumb-bell shape; forming a series 01' ridges in the sheet of metal with the ridges so spaced that wider end portions of each ofsaid apertures lie in the opposite sides of a ridge and the top of the ridge is traversed by a narrow, slot portion connecting said wider portions, bending the ridged sheet to widen a series of said slotted portions, applying a length of tubing laterally into a row of said slotted portions and again bending the. sheet to cause the slotted portions across the ridges, at least partly to overlie the tubing and to retain same in the apertures.

2. In a coil and plate assembly, a plate of conductive material formed to provide a series of spaced parallel ridge portions, the plate being apertured so as to provide paired aligned apertures in opposite sides of each of a plurality of said ridge portions, a length of tubing extending through a series of the aligned apertures, each of said ridge portions being slotted in its upper surface with such slots of lesser width than the tubing diameter and connecting the paired apertures in the opposite sides of the ridge portion, the length of tubing extending through a number of said apertures in the ridge portions, and lying beneath and extended along said slots.

3. The combination and arrangement of elements as recited by claim 2, but further characterized in that the ridge portions consist of right angular substantially parallel walls, transverse to the tubing, and planar, outermost wallconnecting portions, the planes of the connecting portions having a spacing not substantially greater than the diameter of the tubing.

4. In a coil and plate assembly, a plate of conductive material formed to provide a series of spaced parallel flat-top ridge portions, the plate being apertured so as to provide paired aligned apertures in opposite sides of each of a plurality of said ridge portions, a length of tubing extending through a series of the aligned apertures, each of said ridge portions being slotted in its fiattop surface with such slots of lesser width than the tubing diameter and connecting the paired apertures in the opposite sides of the ridge portion, the length of tubing extending through a number of said apertures in the ridge portions, with substantial, spaced lengths of the tubing arranged with side wall portions along and closing said slots, and gripped by the lateral, apertured portions of the ridges to secure the tubing in assembly to the plate.

5. In a coil and plate assembly, a plate of oonductive material formed to provide a series of spaced parallel ridge portions characterized by opposite planar sides, the plate being apertured so as to provide paired aligned apertures in opposite sides of each of a plurality of said ridge portions, 2. length of tubing extending through a series of the aligned apertures, each of said ridge portions being slotted in its upper surface with such slots of lesser width than the tubing diameter and connecting the paired apertures in the opposite sides of the ridge portion, the length of tubing extending through a number of said apertures in theridge-portions, lying beneath and extended along said slots; the sheet metal in the sides of the ridge portions being permanent- 1y compressivelystressed along the. planes of such sides.

6; In a coil and plate assembly, a plate of thermally conductive material formedto provide a. series of spaced parallel ridge portions of a right angular cross-section, with adjacent ridge portions relatively inverted to provide planar tops; bottoms and sidewalls, the plate being apertured soas to provide paired aligned apertures-in planar opposite sides of each of a plurality of said ridge portions, a length of tubing extending through a series of the aligned apertures,

' each of said ridge portions being slotted in its planar top portions, with such slots of lesser Width than the tubing. diameter and connecting the paired apertures in the opposite sides of the ridge portion, the length of tubing extending througha number of said apertures in the ridge portions, successive lengths of the tubing extended along and substantially closing said slots; substantially tangent to the planar slotted tops, and intervening lengths of the tubing beings disposed approximately tangent to theplanar bottoms of the ridge portions, the depth of the ridge portions approximating the diameter of the tubmg.

LOUIS WEISS.

References Cited in the file of this patent UNITED STATES PATENTS- Number Name Date 709,875 Commichau Sept. 30,1902 1,776,080 Murray v Sept. 16, 1930 1,797,030 Steenstrup Mar 17,1931 2,092,170 Kritzer Sept. 7, 1937 2,281,299 Steenstrup Apr. 28, 1942 2,462,511 Kramer Feb. 22, 1949 FOREIGN PATENTS Number Country Date 325,742 Great Britain Feb. 27, 1930 374,306 Great Britain June 9, 1932 

